The present invention relates to press brakes of the type used to shape sheet-like workpieces. More particularly, this invention relates to press brake tool holders that are used to releasably retain forming tools in a press brake.
Press brakes are commonly used to shape sheet-like workpieces, such as sheet metal and the like. A conventional press brake includes an upper table and a lower table, at least one of which is movable toward and away from the other. Typically, the upper table is movable vertically, while the lower table is fixed in a stationary position. It is common for a male forming tool and a female forming die to be carried respectively by the upper and lower tables of a press brake.
Typically, the forming tool has a downwardly-oriented workpiece-deforming surface (or tip). The configuration of this surface is dictated by the shape into which it is desired to bend workpieces. The forming die has a recess that is aligned with the workpiece-deforming surface of the tool. The configuration of the recess corresponds to that of the workpiece-deforming tool surface. Thus, when the tables are brought together, a workpiece between the two is pressed by the tool into the die to give the workpiece the desired bend.
Various tool holders have been devised to mount a forming tool to the upper table of a press brake. For example, U.S. Pat. No. 5,619,885, the teachings of which are incorporated herein by reference, discloses a tool holder with a tool clamp member that is pivotally attached to a stationary support plate. During use, the clamp member exerts a clamping force upon the shank of a forming tool. To keep the tool from falling when the clamping force is released, the clamp member is provided with a projection that is engageable with a complementary drop-prevention groove formed in the tool.
In order to accurately deform workpieces, it is necessary for the forming tool to be mounted securely to the tool holder. This is accomplished by forcibly clamping the tool holder to the forming tool (i.e., by applying a clamping force to the tool). Multiple steps are typically required to operatively mount a forming tool on a conventional tool holder. This is perhaps best understood with reference to FIGS. 1-3, which illustrate a particularly useful press brake tool holder. The illustrated tool holder is disclosed in U.S. Pat. No. 6,003,360, the teachings of which are incorporated herein by reference.
As illustrated in FIG. 1, the forming tool 28 is initially mounted loosely to the tool holder 10. Specifically, the mounting tang 30 of the tool 28 is lifted upwardly between a support plate 14 and a clamp 42 of the tool holder 10. As the tool 28 is moved into the unclamped position illustrated in FIG. 1, a safety slot 122 on the tool 28 is engaged by a lip 116 of the clamp 42. Thus, the tool 28 is prevented from falling from the holder 10 by the engagement of the lip 116 and the safety slot 122. Although the tool 28 is retained loosely by the holder 10 in this position, it is not operatively clamped therein. Specifically, the load-bearing surfaces 24, 26 of the support plate 14 and forming tool 28 are not brought into secure engagement with one another by simply mounting the tool 28 in its unclamped position. Rather, additional steps are required to mount the tool 28 in its operative position.
The upper and lower tables of the press brake are subsequently moved together until the forming tool comes into contact with a forming die on the lower table. This is best understood with reference to FIG. 2, wherein the tip 38 of the loosely-mounted tool 28 has been moved into engagement with a forming die 168 on the lower table (not shown). By forcing the tip 38 of the tool 28 against the die 168, the tool 28 is urged upwardly relative to the tool holder 10 until the load-bearing surface 26 of the tool 28 is moved into contact with the load-bearing surface 24 of the support plate 14.
At this point, the tool 28 can be forcibly clamped (or locked) in its operative position. While maintaining the tool 28 in the position shown in FIG. 2, the lower portion 68 of the clamp 42 is pivoted toward the tool 28. As this portion 68 of the clamp 42 closes upon the shank 30 of the tool 28, the tool is clamped securely to the holder. FIG. 3 illustrates the resulting operative position, wherein the load bearing surfaces 24, 26 of the support plate 14 and the tool 28 are engaged and the mounting shank 30 of the tool 28 is forcibly clamped between the support plate 14 and the lower portion 68 of the clamp 42. During operation, the tool holder 10 is locked in this clamped position. Thus, it can be seen that several steps are typically required to operatively mount a forming tool upon a tool holder.
It would be desirable to provide a tool holder that can be operatively clamped about a forming tool in such a way that the load-bearing surfaces of the tool and the holder are engaged as an adjunct of the clamping action of the tool holder (i.e., without having to press the tip of the loosely-clamped tool against a die on the lower table of the press brake).
A tool holder apparatus for a press brake is provided in a first embodiment of the present invention. The apparatus comprises a support plate having a first receiving surface. A pivotable clamp has an engagement portion that is moveable toward the first receiving surface of the support plate by pivoting the clamp. The engagement portion has therein formed a bore in which a lifting shaft is rotatably received. The engagement portion defines an opening communicating with the bore. The shaft has therein formed a notch that is adapted to be engaged through the opening by an exterior corner of a forming tool. The notch is configured such that when the engagement portion of the clamp is forced against such tool, a first surface of the exterior tool corner bears against a first surface portion of the notch and causes the shaft to rotate within the bore, thereby bringing a second surface portion of the notch to bear against a second surface of the exterior tool corner and delivering to the tool a mounting force having a component normal to the second surface of the exterior tool corner.
In another aspect of the invention, there is provided a tool holder assembly for a press brake. The assembly comprises a support plate having a first receiving surface and a load-bearing receiving surface. A forming tool has a first mounting surface on a first side thereof and an exterior corner (i.e., an exterior tool corner) on a second side thereof. The first mounting surface of the tool is engaged with the first receiving surface of the support plate. The tool has a load-bearing mounting surface forming an included right angle with the first mounting surface. The load-bearing mounting surface is adapted to engage the load-bearing surface of the support plate. A pivotable clamp has an engagement portion that is moveable toward the first receiving surface by pivoting the clamp. The engagement portion has therein formed a bore in which a lifting shaft is rotatably received. The engagement portion defines an opening communicating with the bore. The shaft has therein formed a notch that is adapted to be engaged through the opening by the exterior corner of the forming tool. The notch is configured such that when the engagement portion of the clamp is forced against the tool, a first surface of the exterior tool corner bears against a first surface portion of the notch and causes the shaft to rotate within the bore, thereby bringing a second surface portion of the notch to bear against a second surface of the exterior tool corner. Thus, delivering to the tool a mounting force having a component normal to the second surface of the exterior tool corner.
In still another aspect of the invention, there is provided an upper press brake assembly. The assembly comprises an upper press brake table including a tool holder body. A support plate forms part of the tool holder body and has a first receiving surface and a generally downward-facing load-bearing receiving surface. The receiving surfaces of the support plate together define an exterior corner. A forming tool has a first mounting surface on a first side thereof and an exterior corner (i.e., an exterior tool corner) defined by first and second corner surfaces on a second side thereof. The second corner surface is generally-downwardly-facing. The first mounting surface of the tool is engaged with the first receiving surface of the support plate. The tool has a load-bearing mounting surface forming an included angle with the first mounting surface and being adapted to engage the generally downward-facing load-bearing receiving surface of the support plate. A clamp is attached pivotally to the tool holder body and has an engagement portion that is moveable toward the first receiving surface by pivoting the clamp. The engagement portion has therein formed a bore in which a lifting shaft is rotatably received. The engagement portion defines an opening communicating with the bore. The shaft has therein formed a notch that is adapted to be engaged through the opening by the exterior corner of the tool. The notch is configured such that when the engagement portion of the clamp is forced against the tool, the first corner surface bears against a first surface portion of the notch and causes the shaft to rotate within the bore, thereby bringing a second surface portion of the notch to bear against the second corner surface. Thus, delivering to the tool a mounting force having a generally-upward component.
A tool holder apparatus for a press brake is provided in yet another aspect of the invention. The apparatus comprises a support plate having a first receiving surface and a generally downward-facing receiving surface. These receiving surfaces together define an exterior corner. A pivotable clamp has an engagement portion that is moveable toward the first receiving surface by pivoting the clamp. The engagement portion has therein formed a bore in which a lifting shaft is rotatably carried. The engagement portion defines a slot communicating with the bore. The shaft has therein formed a notch that is adapted to be engaged through the slot by an exterior corner of a forming tool a mounting tang of which is positioned between the first receiving surface of the support plate and the engagement portion of the clamp. The notch is configured such that when the engagement portion of the clamp is forced against such tool, a generally-vertical surface of the exterior corner bears against a first surface portion of the notch and causes the shaft to rotate within the bore, thereby bringing a second surface portion of the notch to bear against a generally-downward-facing surface of the exterior corner and delivering to the tool a mounting force having a generally-upward component.
A tool holder apparatus for a press brake is provided in still another aspect of the invention. The apparatus comprises a support plate having a first receiving surface. A clamp has an engagement portion defining a slot communicating with a bore formed in the clamp. A lifting shaft is rotatably received in the bore. The shaft has therein formed a notch that can be engaged through the slot by an exterior corner of a forming tool. The notch is configured such that when it is forced against the exterior corner, a first surface of the exterior corner bears against a first surface portion of the notch and causes the shaft to rotate within the bore, thereby bringing a second surface portion of the notch to bear against a second surface of the exterior corner. Thus, delivering to the tool a mounting force having a component normal to the second surface of said exterior corner.
In yet another aspect of the invention, there is provided a press brake assembly. The assembly comprises an upper press brake table including a tool holder body and a lower press brake table including a forming die. A support plate forms part of the tool holder body and has a first receiving surface and a load-bearing receiving surface. These receiving surfaces together form an exterior corner. A forming tool has a first mounting surface on a first side thereof and an exterior corner defined by first and second corner surfaces on a second side of the tool. The first mounting surface is engaged with the first receiving surface of the support plate. The tool has a load-bearing mounting surface forming an included angle with the first mounting surface. The load-bearing mounting surface is adapted to engage the load-bearing surface of the support plate. The tool has a workpiece-deforming surface oriented downwardly toward the forming die. A clamp is attached pivotally to the tool holder body and has an engagement portion that is moveable toward said first receiving surface by pivoting the clamp. The engagement portion has therein formed a bore in which an elongated shaft is rotatably received. The engagement portion defines an opening communicating with the bore. The shaft has therein formed a notch that is adapted to be engaged through the opening by the exterior corner of the tool. The notch is configured such that when the engagement portion of the clamp is forced against the tool, the first corner surface bears against a first surface portion of the notch and causes the shaft to rotate within the bore, thereby bringing a second surface portion of the notch to bear against the second corner surface and delivering to the tool a mounting force having a component normal to the second corner surface. Thus, the load-bearing surfaces can be engaged with one another by forcing the engagement portion of the clamp against the tool without forcing the workpiece-deforming surface of the tool against the forming die on the lower table.